This invention relates to a new and novel method for the production of chip resistors.
Chip resistors are small film resistors formed of thick dabs of resistive material in contact with conductive metal pads all deposited on a surface of a small piece or chip of an insulating ceramic substrate such as aluminum oxide substrate.
These chip resistors may be employed as resistors in printed circuit boards.
In order to provide a leadless electrical contact with other components with these printed circuit boards the chip resistors are provided with thin conductive metal bands or edge-around terminations each of which is in contact with one of the metal pads and extends over an edge, and sometimes to the rear surface of the chip. Through these edge-around terminations the chip resistors are electrically connected and secured in the printed circuit board by such techniques such as wave soldering, the use of clamps or, in some cases a combination of both.
Such chip resistors are well known in the art and are described for example in Electronics, Aug. 16, 1979, pp. 72-73.
In the method usually employed in producing the chip resistors, series of rows of conductive metal pads and the connecting dabs of resistance material are deposited on a surface of a large sheet of an alumina substrate, generally by using a screening and firing technique. A protective glass coat is then applied and the thin substrate is then separated into large rows of chips.
The rows of chips are then stacked and the edge around terminators are then applied by a screening or dipping technique followed by firing at a high-temperature, frequently at 815.degree. C.-900.degree. C., to fire the edge around terminators.
Because of the high temperature employed in forming the edge-around terminations by this means laser-trimming cannot be carried out until each chip resistor is separated. Because the laser trimming must be then carried out on each chip separately the production rate is low and in some cases so low as to be economically unsatisfactory.
However, while laser trimming of a number of resistors in a resistor network prior to application of mechanically connected terminals is known in the art, as shown by Kost et al U.S. Pat. No. 4,159,461, there is no teaching in the art of a method for the production of chip resistors furnished with permanently attached edge-around terminations formed by a deposition process in which laser trimming is carried out while all the resistors are still present on the substrate.